Fine dissection electrosurgical device

ABSTRACT

An electrosurgical wand. At least some of the illustrative embodiments are electrosurgical wands including an elongate shaft that defines a handle end and a distal end, a first discharge aperture on the distal end of the elongate shaft, a first active electrode of conductive material disposed on the distal end of the elongate shaft, the first active electrode has an edge feature, a first return electrode of conductive material disposed a substantially constant distance from the first active electrode, and an aspiration aperture on the distal end of the elongate shaft fluidly coupled to a second fluid conduit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 13/023,603 filed Feb. 9, 2011 and entitled “Fine Dissection Electrosurgical Device” hereby incorporated herein by reference.

BACKGROUND

The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on a separate electrode for the return of current that is placed away from the surgical site on the body of the patient, and where the surgical device defines only a single electrode pole that provides the surgical effect. Bipolar devices comprise two or more electrodes on the same support for the application of current between their surfaces.

Electrosurgical procedures and techniques are particularly advantageous since they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities.

Radiofrequency (RF) energy is used in a wide range of surgical procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. Conventional monopolar high frequency electrosurgical devices typically operate by creating a voltage difference between the active electrode and the target tissue, causing an electrical arc to form across the physical gap between the electrode and tissue. At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue. This high current density causes cellular fluids to rapidly vaporize into steam, thereby producing a “cutting effect” along the pathway of localized tissue heating. Thus, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site. This collateral tissue damage often causes indiscriminate destruction of tissue, resulting in the loss of the proper function of the tissue. In addition, the device does not remove any tissue directly, but rather depends on destroying a zone of tissue and allowing the body to eventually remove the destroyed tissue.

Present electrosurgical techniques used for tissue ablation may suffer from an inability to provide the ability for fine dissection of soft tissue. The distal end of electrosurgical devices is wide and flat, creating a relatively wide area of volumetric tissue removal and making fine dissections along tissue planes more difficult to achieve because of the lack of precision provided by the current tip geometries. In addition, identification of the plane is more difficult because the large ablated area and overall size of the device tip obscures the physician's view of the surgical field. The inability to provide for fine dissection of soft tissue is a significant disadvantage in using electrosurgical techniques for tissue ablation, particularly in arthroscopic, otolaryngological, and spinal procedures.

Traditional monopolar RF systems can provide fine dissection capabilities of soft tissue, but may also cause a high level of collateral thermal damage. Further, these devices may suffer from an inability to control the depth of necrosis in the tissue being treated. The high heat intensity generated by these systems causes burning and charring of the surrounding tissue, leading to increased pain and slower recovery of the remaining tissue. Further, the desire for an electrosurgical device to provide for fine dissection of soft tissue may compromise the ability to provide consistent ablative cutting without significant collateral damage while allowing for concomitant hemostasis and good coagulation of the remaining tissue.

Accordingly, improved systems and methods are still desired for performing fine dissection of soft tissue via electrosurgical ablation of tissue. In particular, improved systems operable to provide a combination of smooth and precise cutting, effective concomitant hemostasis during cutting, and efficient coagulation ability in fine dissection soft tissue procedures would provide a competitive advantage.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 shows an electrosurgical system in accordance with at least some embodiments;

FIG. 2A shows a perspective view a portion of a wand in accordance with at least some embodiments;

FIG. 2B shows an end elevation view of a wand in accordance with at least some embodiments;

FIG. 2C shows a cross-sectional view of a wand in accordance with at least some embodiments;

FIG. 3A shows a side elevation view of a wand in accordance with at least some embodiments;

FIG. 3B shows a side elevation view of a wand in accordance with at least some embodiments;

FIG. 3C shows a cross-sectional view of a wand in accordance with at least some embodiments;

FIG. 4A shows a cross-sectional view of a wand in accordance with at least some embodiments;

FIG. 4B shows a cross-sectional view of a wand in accordance with at least some embodiments;

FIG. 5 shows both an elevational end-view (left) and a cross-sectional view (right) of a wand connector in accordance with at least some embodiments;

FIG. 6 shows both an elevational end-view (left) and a cross-sectional view (right) of a controller connector in accordance with at least some embodiments;

FIG. 7 shows an electrical block diagram of an electrosurgical controller in accordance with at least some embodiments; and

FIG. 8 shows a method in accordance with at least some embodiments.

FIG. 9 shows a perspective view of a portion of a wand in accordance with at least some embodiments;

FIG. 10A shows a side elevation view of an inferior side of a wand distal end, in accordance with at least some embodiments;

FIG. 10B shows a side elevation view of a superior side of a wand distal end, in accordance with at least some embodiments;

FIG. 11A shows a wand treating a target tissue in accordance with at least some embodiments;

FIG. 11B shows a wand treating a target tissue in accordance with at least some embodiments;

FIG. 12 shows a method of treating tissue in accordance with at least some embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, companies that design and manufacture electrosurgical systems may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . . ” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect electrical connection via other devices and connections.

Reference to a singular item includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “an,” “said” and “the” include plural references unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement serves as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Lastly, it is to be appreciated that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

“Active electrode” shall mean an electrode of an electrosurgical wand which produces an electrically-induced tissue-altering effect when brought into contact with, or close proximity to, a tissue targeted for treatment.

“Return electrode” shall mean an electrode of an electrosurgical wand which serves to provide a current flow path for electrons with respect to an active electrode, and/or an electrode of an electrical surgical wand which does not itself produce an electrically-induced tissue-altering effect on tissue targeted for treatment.

A fluid conduit said to be “within” an elongate shaft shall include not only a separate fluid conduit that physically resides within an internal volume of the elongate shaft, but also situations where the internal volume of the elongate shaft is itself the fluid conduit.

Where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein.

All existing subject matter mentioned herein (e.g., publications, patents, patent applications and hardware) is incorporated by reference herein in its entirety except insofar as the subject matter may conflict with that of the present invention (in which case what is present herein shall prevail). The referenced items are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such material by virtue of prior invention.

DETAILED DESCRIPTION

Before the various embodiments are described in detail, it is to be understood that this invention is not limited to particular variations set forth herein as various changes or modifications may be made, and equivalents may be substituted, without departing from the spirit and scope of the invention. As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. All such modifications are intended to be within the scope of the claims made herein.

FIG. 1 illustrates an electrosurgical system 100 in accordance with at least some embodiments. In particular, the electrosurgical system comprises an electrosurgical wand 102 (hereinafter “wand”) coupled to an electrosurgical controller 104 (hereinafter “controller”). The wand 102 comprises an elongate shaft 106 that defines distal end 108 where at least some electrodes are disposed. The elongate shaft 106 further defines a handle or proximal end 110, where a physician grips the wand 102 during surgical procedures. The wand 102 further comprises a flexible multi-conductor cable 112 housing a plurality of electrical leads (not specifically shown in FIG. 1), and the flexible multi-conductor cable 112 terminates in a wand connector 114. As shown in FIG. 1, the wand 102 couples to the controller 104, such as by a controller connector 120 on an outer surface 122 (in the illustrative case of FIG. 1, the front surface).

Though not visible in the view of FIG. 1, in some embodiments the wand 102 has one or more internal fluid conduits coupled to externally accessible tubular members. As illustrated, the wand 102 has a flexible tubular member 116 and a second flexible tubular member 118. In some embodiments, the flexible tubular member 116 is used to provide electrically conductive fluid (e.g., saline) to the distal end 108 of the wand. Likewise in some embodiments, flexible tubular member 118 is used to provide aspiration to the distal end 108 of the wand.

Still referring to FIG. 1, a display device or interface panel 124 is visible through the outer surface 122 of the controller 104, and in some embodiments a user may select operational modes of the controller 104 by way of the interface device 124 and related buttons 126.

In some embodiments the electrosurgical system 100 also comprises a foot pedal assembly 130. The foot pedal assembly 130 may comprise one or more pedal devices 132 and 134, a flexible multi-conductor cable 136 and a pedal connector 138. While only two pedal devices 132, 134 are shown, one or more pedal devices may be implemented. The outer surface 122 of the controller 104 may comprise a corresponding connector 140 that couples to the pedal connector 138. A physician may use the foot pedal assembly 130 to control various aspects of the controller 104, such as the operational mode. For example, a pedal device, such as pedal device 132, may be used for on-off control of the application of radio frequency (RF) energy to the wand 102, and more specifically for control of energy in an ablation mode. A second pedal device, such as pedal device 134, may be used to control and/or set the operational mode of the electrosurgical system. For example, actuation of pedal device 134 may switch between energy levels of an ablation mode.

The electrosurgical system 100 of the various embodiments may have a variety of operational modes. One such mode employs Coblation® technology. In particular, the assignee of the present disclosure is the owner of Coblation® technology. Coblation technology involves the application of a radio frequency (RF) signal between one or more active electrodes and one or more return electrodes of the wand 102 to develop high electric field intensities in the vicinity of the target tissue. The electric field intensities may be sufficient to vaporize an electrically conductive fluid over at least a portion of the one or more active electrodes in the region between the one or more active electrodes and the target tissue. The electrically conductive fluid may be inherently present in the body, such as blood, or in some cases extracellular or intracellular fluid. In other embodiments, the electrically conductive fluid may be a liquid or gas, such as isotonic saline. In some embodiments, such as surgical procedures on a disc between vertebrae, the electrically conductive fluid is delivered in the vicinity of the active electrode and/or to the target site by the wand 102, such as by way of the internal passage and flexible tubular member 116.

When the electrically conductive fluid is heated to the point that the atoms of the fluid vaporize faster than the atoms recondense, a gas is formed. When sufficient energy is applied to the gas, the atoms collide with each other causing a release of electrons in the process, and an ionized gas or plasma is formed (the so-called “fourth state of matter”). Stated otherwise, plasmas may be formed by heating a gas and ionizing the gas by driving an electric current through the gas, or by directing electromagnetic waves into the gas. The methods of plasma formation give energy to free electrons in the plasma directly, electron-atom collisions liberate more electrons, and the process cascades until the desired degree of ionization is achieved. A more complete description of plasma can be found in Plasma Physics, by R. J. Goldston and P. H. Rutherford of the Plasma Physics Laboratory of Princeton University (1995), the complete disclosure of which is incorporated herein by reference.

As the density of the plasma becomes sufficiently low (i.e., less than approximately 1020 atoms/cm³ for aqueous solutions), the electron mean free path increases such that subsequently injected electrons cause impact ionization within the plasma. When the ionic particles in the plasma layer have sufficient energy (e.g., 3.5 electron-Volt (eV) to 5 eV), collisions of the ionic particles with molecules that make up the target tissue break molecular bonds of the target tissue, dissociating molecules into free radicals which then combine into gaseous or liquid species. Often, the electrons in the plasma carry the electrical current or absorb the electromagnetic waves and, therefore, are hotter than the ionic particles. Thus, the electrons, which are carried away from the target tissue toward the active or return electrodes, carry most of the plasma's heat, enabling the ionic particles to break apart the target tissue molecules in a substantially non-thermal manner.

By means of the molecular dissociation (as opposed to thermal evaporation or carbonization), the target tissue is volumetrically removed through molecular dissociation of larger organic molecules into smaller molecules and/or atoms, such as hydrogen, oxygen, oxides of carbon, hydrocarbons and nitrogen compounds. The molecular dissociation completely removes the tissue structure, as opposed to dehydrating the tissue material by the removal of liquid within the cells of the tissue and extracellular fluids, as occurs in related art electrosurgical desiccation and vaporization. A more detailed description of the molecular dissociation can be found in commonly assigned U.S. Pat. No. 5,697,882, the complete disclosure of which is incorporated herein by reference.

In addition to the Coblation mode, the electrosurgical system 100 of FIG. 1 may also in particular situations be useful for sealing larger arterial vessels (e.g., on the order of about 1 mm in diameter), when used in what is known as a coagulation mode. Thus, the system of FIG. 1 may have an ablation mode where RF energy at a first voltage is applied to one or more active electrodes sufficient to effect molecular dissociation or disintegration of the tissue, and the system of FIG. 1 may have a coagulation mode where RF energy at a second, lower voltage is applied to one or more active electrodes (either the same or different electrode(s) as the ablation mode) sufficient to heat, shrink, seal, fuse, and/or achieve homeostasis of severed vessels within the tissue.

The energy density produced by electrosurgical system 100 at the distal end 108 of the wand 102 may be varied by adjusting a variety of factors, such as: the number of active electrodes; electrode size and spacing; electrode surface area; asperities and/or sharp edges on the electrode surfaces; electrode materials; applied voltage; current limiting of one or more electrodes (e.g., by placing an inductor in series with an electrode); electrical conductivity of the fluid in contact with the electrodes; density of the conductive fluid; and other factors. Accordingly, these factors can be manipulated to control the energy level of the excited electrons. Because different tissue structures have different molecular bonds, the electrosurgical system 100 may be configured to produce energy sufficient to break the molecular bonds of certain tissue but insufficient to break the molecular bonds of other tissue. For example, fatty tissue (e.g., adipose) has double bonds that require an energy level higher than 4 eV to 5 eV (i.e., on the order of about 8 eV) to break. Accordingly, the Coblation® technology in some operational modes does not ablate such fatty tissue; however, the Coblation® technology at the lower energy levels may be used to effectively ablate cells to release the inner fat content in a liquid form. Other modes may have increased energy such that the double bonds can also be broken in a similar fashion as the single bonds (e.g., increasing voltage or changing the electrode configuration to increase the current density at the electrodes).

A more complete description of the various phenomena can be found in commonly assigned U.S. Pat. Nos. 6,355,032; 6,149,120 and 6,296,136, the complete disclosures of which are incorporated herein by reference.

FIG. 2A illustrates a perspective view of the distal end 108 of wand 102 in accordance with at least some embodiments. In some embodiments, a portion of the elongate shaft 106 may be made of a metallic material (e.g., Grade TP304 stainless steel hypodermic tubing). In other embodiments, portions of the elongate shaft may be constructed of other suitable materials, such as inorganic insulating materials. The elongate shaft 106 may define a circular cross-section at the handle or proximal end 110 (not shown in FIG. 2), and at least a portion of the distal end 108 may be flattened to define an elliptical or semi-circular cross-section.

In embodiments where the elongate shaft is metallic, the distal end 108 may further comprise a non-conductive spacer 200 coupled to the elongate shaft 106. In some cases the spacer 200 is ceramic, but other non-conductive materials resistant to degradation when exposed to plasma may be equivalently used (e.g., glass). The spacer 200 supports electrodes of conductive material, with illustrative active electrode labeled 202 in FIG. 2A. Active electrode 202 defines an exposed surface area of conductive material, where active electrode 202 is a loop of wire of particular diameter. For embodiments using a loop of wire, the loop of wire may be molybdenum or tungsten having a diameter between and including 0.025 and 0.035 inches, and more preferably of 0.030 inches, and having an exposed standoff distance away from the spacer 200 of approximately 0.080 inches. Spacer 200 may have a step feature 201 that serves to limit the depth of penetration of active electrode 202 by providing a non-conductive surface to rest on adjacent tissue, thereby allowing for a more controlled and precise cut as well as providing for a more uniform depth of thermal effect in tissue. Further, spacer 200 may define an elliptical or semi-circular cross-section to provide a flattened support profile for active electrode 202.

In certain embodiments, the active electrode has an edge feature 203 at a specific, distinct location advantageous for enhanced plasma formation. In particular, active electrode 202 may be defined by an edge feature 203 (e.g., a scalloped portion, a cut, divot, or asperity) having a cut diameter and depth between and including 0.008 and 0.0012 inches, and more preferably of approximately 0.010 inches on each side, leaving a thin segment of approximately 0.010 inches thickness in the central portion of active electrode 202. Referring to FIG. 2B, edge feature 203 is preferably located in at least two positions on opposed sides of a plane P₁ bisecting the wire diameter of active electrode 202, and centered about a second plane P₂ bisecting the width of active electrode 202. FIG. 2C shows a cross-sectional view of active electrode 202 and spacer 200 taken substantially along plane P₂ of FIG. 2B. In particular, FIG. 2C shows the orientation of edge feature 203 in an embodiment where the feature is a pair of symmetric cuts in active electrode 202. In certain other embodiments contemplated but not shown, edge feature 203 can also be a protruding section along active electrode 202 formed through a coining, welding, or other forming operation to provide exterior edges for improved localized plasma formation in these areas. Edge feature 203 at the distal tip of active electrode 202 helps initiate localized plasma formation in the relative center of active electrode 202 for smooth cutting. Referring briefly to FIGS. 3A and 3B, active electrode 202 further has rounded edges or a smooth feature 203 b at a second, distinct location away from edge feature 203 for conductive/resistive heating of tissue at locations spaced away from edge feature 203. In particular, active electrode 202 may be loop of wire characterized by edge feature 203 at the apex of the loop and smooth feature 203 b adjacent to edge feature 203 and disposed on either side of the loop forming active electrode 202. This conductive heating of surrounding tissue helps provide concomitant hemostasis of small blood vessels while plasma is initiated for cutting.

Referring again to FIG. 2A, wand 102 includes a return electrode 204 for completing the current path between active electrode 202 and controller 104. Return electrode 204 is preferably a semi-annular member defining the exterior of shaft 106, and a distal portion of return electrode 204 is preferably exposed. Return electrode 204 is suitably connected to controller 104. At least a proximal portion of return electrode 204 is disposed within an electrically insulative sheath 206, which is typically formed as one or more electrically insulative sheaths or coatings, such as polytetrafluoroethylene, polyimide, and the like. The provision of the electrically insulative sheath 206 encircling over a portion of return electrode 204 prevents direct electrical contact between return electrode 204 and any adjacent body structure or the surgeon. Such direct electrical contact between a body structure (e.g., tendon) and an exposed common electrode member 204 could result in unwanted heating and necrosis of the structure at the point of contact causing necrosis.

Return electrode 204 is preferably formed from an electrically conductive material, usually metal, which is selected from the group consisting of stainless steel alloys, platinum or its alloys, titanium or its alloys, molybdenum or its alloys, and nickel or its alloys. Referring now to FIG. 3A, the distance D between active electrode 202 and return electrode 204 is preferably kept substantially constant. As such, it is preferred that the distal projection of return electrode 204 have a non-uniform shape to approximate the geometry of active electrode 202. In a preferred embodiment, return electrode 204 has an extended feature in the form of tab 205 extending distally. This extension tab 205 maintains a near-uniform distance between the active loop electrode 202 and return electrode 204. Preferably, the extended tab 205 closes the distance between the return electrode 204 and the active electrode 202 as measured at the apex of the active loop electrode 202, thereby keeping the distance D between all portions of the active and return electrodes substantially constant. It also brings the distal end of the return electrode 204 closer to the targeted tissue to improve the conduction of current through tissue and saline between the active and return electrodes. This enables a more uniform and continuous delivery of electrical current through the targeted tissue during coagulation mode, providing greater depth of thermal penetration for improved coagulation of blood vessels.

In some embodiments saline is delivered to the distal end 108 of wand, possibly to aid in plasma creation. Referring again to FIGS. 2A and 2B, discharge apertures 208 are illustrated on the distal end 108 spaced proximally from return electrode 204. Discharge apertures 208 are formed at the distal most point of the insulative sheath 206 encircling a portion of return electrode 204. Insulative sheath 206 further creates an annular gap between the insulative sheath and return electrode 204, in which multiple axially disposed ribs are spaced equally throughout to form a plurality of fluid flow channels 209 that direct discharged conductive fluid toward the return electrode 204 and active electrode 202. Discharge apertures 208 characterize the distal most opening of the associated plurality of flow channels 209. In the particular embodiment illustrated, eight discharge apertures are shown, but fewer or greater numbers of discharge apertures are contemplated. The discharge apertures 208 are fluidly coupled to the flexible tubular member 116 (FIG. 1) by way of a fluid conduit within the wand 102. Thus, saline or other fluid may be pumped into the flexible tubular member 116 (FIG. 1) and discharged through the plurality of fluid flow channels 209 and discharge apertures 208 to further aid in developing consistent wetting around the circumference of return electrode 204.

In yet still further embodiments, aspiration is provided at the distal end 108 of the wand 102. FIG. 3B illustrates aspiration aperture 207 (i.e., suction port 207) at the distal end 108 of the device and disposed through the non-conductive spacer 200 and defining in part an opening in return electrode 204. Suction port 207 is disposed at distal end 108 and in certain embodiments preferably only located on one side of spacer 200 and disposed on an inferior surface of spacer 200 (such that when in use the suction port 207 is preferably disposed inferiorly with regard to the angle of approach to the target tissue), and accordingly may be disposed on the opposite side of spacer 200 from tab 205. Suction port 207 aspirates the area near the distal end 108, such as to remove excess fluids and remnants of ablation. The location of suction port 207 further provides for ample wetting of the active and return electrodes on the opposing side of the tip, with the saline flowing down from discharge apertures 208 on the non-suction side of the shaft, around the active electrode tip, then pulled back up on the inferior side of the wand with suction port 207. Applicants have found it is particularly beneficial to direct conductive fluid flow to discrete areas away from the suction port 207 to provide broader wetting of the exposed surface of return electrode 204, enabling more uniform plasma formation.

Additionally, referring briefly to both FIGS. 2B and 3B, suction port 207 may be offset inferior from plane P₁, which also bisects the thickness T of distal end 108 of elongate shaft 106. FIG. 3C shows a cross-section view taken substantially along plane P₁ of FIG. 2B. In particular, FIG. 3C shows suction port 207 as well as spacer fluid conduit 210 defined by walls 212. Fluid conduit 210 further comprises an aspiration chamber 216 having a fluid conduit opening 214. In operation, suction is provided to the flexible tubular member 118 (FIG. 1), and flexible tubular member 118 either extends into the internal volume of the wand 102 to become, or fluidly couples to, opening 214 of aspiration chamber 216. Thus, conductive fluid, molecularly dissociated tissue, as well as tissue pieces are drawn through the suction port 207, into the fluid conduit 210, and eventually through aspiration chamber 216 and opening 214. Aspiration chamber 216 is spaced proximally from suction port 207, and the inventors of the present specification have found that a particular depth of aspiration chamber 216 and width of opening 214 work better than others. For example, without the increased area of aspiration chamber 216, the fluid conduit 210 may be subject to clogging. Likewise, if the coupling point for flexible tubular member 118 at opening 114 does not have an increased diameter, clogging may occur. In accordance with at least some embodiments, the nature of fluid conduit 210 transitions over a length L between suction port 207 and opening 214. The entrance to the fluid conduit 210 is referenced by an aspiration aperture width W_(a). In accordance with at least some embodiments the internal walls 212 that define fluid conduit 210 smoothly transition to a change in width referenced by an opening width W_(o) at opening 214 over length L wherein the width change to W_(o) at opening 214 should be at least half the full ID of the shaft. Additionally, referring again now to FIG. 2C, the depth of fluid conduit 210 as it transitions to aspiration chamber 216 should smoothly vary at least to a depth referenced by depth D_(c), wherein the apex of depth D_(c) should be at least half the thickness T (FIG. 2B) of spacer 200 and then smoothly transitioning to a depth D_(o) at opening 214. The inventors present the nature of fluid conduit 210 as described above by way of example only. Other variances and transitions in the shape, respective widths, and depths of portions of fluid conduit 210 and aspiration chamber 216 from suction port 207 to opening 214 may be equivalently used.

As shown for example in FIGS. 2A-3B, return electrode 204 is not directly connected to active electrode 202. To complete a current path so that active electrode 202 is electrically connected to return electrode 204 in the presence of a target tissue, electrically conducting liquid (e.g., isotonic saline) is caused to flow along liquid paths emanating from discharge apertures 208 and contacting both return electrode 204 and active electrode 202. When a voltage difference is applied between active electrode 202 and return electrode 204, high electric field intensities will be generated at the distal tip of active electrode 202 with current flow from active electrode 202 to the return electrode 204, the high electric field intensities causing ablation of target tissue adjacent the distal tip of active electrode 202.

FIG. 4A shows a cross-sectional elevation view of a wand 102 in accordance with at least some embodiments. In particular, FIG. 4A shows the handle or proximal end 110 coupled to the elongate shaft 106. As illustrated, the elongate shaft 106 telescopes within the handle, but other mechanisms to couple the elongate shaft to the handle may be equivalently used. The elongate shaft 106 defines internal conduit 400 that serves several purposes. For example, in the embodiments illustrated by FIG. 4A the electrical leads 402 and 404 extend through the internal conduit 400 to electrically couple to the active electrode 202 and return electrode 204, respectively. Likewise, the flexible tubular member 116 extends through the internal conduit 400 to fluidly couple to the plurality of flow channels 209 and discharge apertures 208 via insulative sheath 206.

The internal conduit 400 also serves as the aspiration route. In particular, FIG. 4B illustrates suction port 207. In the embodiments illustrated the flexible tubular member 118, through which aspiration is performed, couples through the handle and then fluidly couples to the internal conduit 400. Thus, the suction provided through flexible tubular member 118 provides aspiration at the suction port 207. The fluids that are drawn into the internal fluid conduit 400 may abut the portion of the flexible tubular member 116 that resides within the internal conduit as the fluids are drawn along the conduit; however, the flexible tubular member 116 is sealed, and thus the aspirated fluids do not mix with the fluid (e.g., saline) being pumped through the flexible tubular member 116. Likewise, the fluids that are drawn into the internal fluid conduit 400 may abut portions of the electrical leads 402 and 404 within the internal fluid conduit 400 as the fluids are drawn along the conduit. However, the electrical leads are insulated with an insulating material that electrically and fluidly isolates the leads from any substance within the internal fluid conduit 400. Thus, the internal fluid conduit serves, in the embodiments shown, two purposes—one to be the pathway through which the flexible tubular member 116 and electrical leads traverse to reach the distal end 108, and also as the conduit through which aspiration takes place. In other embodiments, the flexible tubular member 118 may extend partially or fully through the elongate shaft 106, and thus more directly couple to the aspiration apertures.

FIGS. 4A and 4B also illustrate that, in accordance with at least some embodiments, a portion of the elongate shaft 106 is circular (e.g., portion 410) and another portion of the elongate shaft 106 is flattened (e.g., portion 412) to define an elliptical or semi-circular cross-section. In some embodiments, the distal 3 centimeters or less is flattened, and in some cases the last 2 centimeters. In other embodiments, the entire elongate shaft may define the elliptical or semi-circular cross-section. Additionally, in the particular embodiments illustrated the angle between the axis of portion 410 and the axis of portion 412 is non-zero, and in some embodiments the acute angle between the axis of portion 410 and the axis of portion 412 is 20 degrees, but greater or lesser angles may be equivalently used.

As illustrated in FIG. 1, flexible multi-conductor cable 112 (and more particularly its constituent electrical leads 402, 404 and possibly others) couple to the wand connector 114. Wand connector 114 couples the controller 104, and more particularly the controller connector 120. FIG. 5 shows both a cross-sectional view (right) and an end elevation view (left) of wand connector 114 in accordance with at least some embodiments. In particular, wand connector 114 comprises a tab 500. Tab 500 works in conjunction with a slot on controller connector 120 (shown in FIG. 6) to ensure that the wand connector 114 and controller connector 120 only couple in one relative orientation. The illustrative wand connector 114 further comprises a plurality of electrical pins 502 protruding from wand connector 114. In many cases, the electrical pins 502 are coupled one each to an electrical lead of electrical leads 504 (two of which may be leads 402 and 404 of FIG. 4A and FIG. 4B). Stated otherwise, in particular embodiments each electrical pin 502 couples to a single electrical lead, and thus each illustrative electrical pin 502 couples to a single electrode of the wand 102. In other cases, a single electrical pin 502 couples to multiple electrodes on the electrosurgical wand 102. While FIG. 5 shows four illustrative electrical pins, in some embodiments as few as two electrical pins, and as many as 26 electrical pins, may be present in the wand connector 114.

FIG. 6 shows both a cross-sectional view (right) and an end elevation view (left) of controller connector 120 in accordance with at least some embodiments. In particular, controller connector 120 comprises a slot 600. Slot 600 works in conjunction with a tab 500 on wand connector 114 (shown in FIG. 5) to ensure that the wand connector 114 and controller connector 120 only couple in one orientation. The illustrative controller connector 120 further comprises a plurality of electrical pins 602 residing within respective holes of controller connector 120. The electrical pins 602 are coupled to terminals of a voltage generator within the controller 104 (discussed more thoroughly below). When wand connector 114 and controller connector 120 are coupled, each electrical pin 602 couples to a single electrical pin 502. While FIG. 6 shows only four illustrative electrical pins, in some embodiments as few as two electrical pins, and as many as 26 electrical pins may be present in the wand connector 120.

While illustrative wand connector 114 is shown to have the tab 500 and male electrical pins 502, and controller connector 120 is shown to have the slot 600 and female electrical pins 602, in alternative embodiments the wand connector has the female electrical pins and slot, and the controller connector 120 has the tab and male electrical pins, or other combination. In other embodiments, the arrangement of the pins within the connectors may enable only a single orientation for connection of the connectors, and thus the tab and slot arrangement may be omitted. In yet still other embodiments, other mechanical arrangements to ensure the wand connector and controller connector couple in only one orientation may be equivalently used. In the case of a wand with only two electrodes, and which electrodes may be either active or return electrodes as the physical situation dictates, there may be no need to ensure the connectors couple in a particular orientation.

FIG. 7 illustrates a controller 104 in accordance with at least some embodiments. In particular, the controller 104 comprises a processor 700. The processor 700 may be a microcontroller, and therefore the microcontroller may be integral with random access memory (RAM) 702, read-only memory (RAM) 704, digital-to-analog converter (D/A) 706, digital outputs (D/O) 708 and digital inputs (D/I) 710. The processor 700 may further provide one or more externally available peripheral busses, such as a serial bus (e.g., I²C), parallel bus, or other bus and corresponding communication mode. The processor 700 may further be integral with a communication logic 712 to enable the processor 700 to communicate with external devices, as well as internal devices, such as display device 124. Although in some embodiments the controller 104 may implement a microcontroller, in yet other embodiments the processor 700 may be implemented as a standalone central processing unit in combination with individual RAM, ROM, communication, D/A, D/O and D/I devices, as well as communication port hardware for communication to peripheral components.

ROM 704 stores instructions executable by the processor 700. In particular, the ROM 704 may comprise a software program that implements the various embodiments of periodically reducing voltage generator output to change position of the plasma relative to the electrodes of the wand (discussed more below), as well as interfacing with the user by way of the display device 124 and/or the foot pedal assembly 130 (FIG. 1). The RAM 702 may be the working memory for the processor 700, where data may be temporarily stored and from which instructions may be executed. Processor 700 couples to other devices within the controller 104 by way of the D/A converter 706 (e.g., the voltage generator 716), digital outputs 708 (e.g., the voltage generator 716), digital inputs 710 (i.e., push button switches 126, and the foot pedal assembly 130 (FIG. 1)), and other peripheral devices.

Voltage generator 716 generates selectable alternating current (AC) voltages that are applied to the electrodes of the wand 102. In the various embodiments, the voltage generator defines two terminals 724 and 726. In accordance with the various embodiments, the voltage generator generates an alternating current (AC) voltage across the terminals 724 and 726. In at least some embodiments the voltage generator 716 is electrically “floated” from the balance of the supply power in the controller 104, and thus the voltage on terminals 724, 726, when measured with respect to the earth ground or common (e.g., common 728) within the controller 104, may or may not show a voltage difference even when the voltage generator 716 is active.

The voltage generated and applied between the active terminal 724 and return terminal 726 by the voltage generator 716 is a RF signal that, in some embodiments, has a frequency of between about 5 kilo-Hertz (kHz) and 20 Mega-Hertz (MHz), in some cases being between about 30 kHz and 2.5 MHz, often between about 100 kHz and 200 kHz. In applications associated with otolaryngology-head and neck procedures, a frequency of about 100 kHz appears most effective. The RMS (root mean square) voltage generated by the voltage generator 716 may be in the range from about 5 Volts (V) to 1000 V, preferably being in the range from about 10 V to 500 V, often between about 100 V to 350 V depending on the active electrode size and the operating frequency. The peak-to-peak voltage generated by the voltage generator 716 for ablation or cutting in some embodiments is a square wave form in the range of 10 V to 2000 V and in some cases in the range of 100 V to 1800 V and in other cases in the range of about 28 V to 1200 V, often in the range of about 100 V to 320 V peak-to-peak (again, depending on the electrode size and the operating frequency).

Still referring to the voltage generator 716, the voltage generator 716 delivers average power levels ranging from several milliwatts to hundreds of watts per electrode, depending on the voltage applied for the target tissue being treated, and/or the maximum allowed temperature selected for the wand 102. The voltage generator 716 is configured to enable a user to select the voltage level according to the specific requirements of a particular procedure. A description of one suitable voltage generator 716 can be found in commonly assigned U.S. Pat. Nos. 6,142,992 and 6,235,020, the complete disclosure of both patents are incorporated herein by reference for all purposes.

In some embodiments, the various operational modes of the voltage generator 716 may be controlled by way of digital-to-analog converter 706. That is, for example, the processor 700 may control the output voltage by providing a variable voltage to the voltage generator 716, where the voltage provided is proportional to the voltage generated by the voltage generator 716. In other embodiments, the processor 700 may communicate with the voltage generator by way of one or more digital output signals from the digital output 708 device, or by way of packet based communications using the communication device 712 (connection not specifically shown so as not to unduly complicate FIG. 8).

FIG. 7 also shows a simplified side view of the distal end 108 of the wand 102. As shown, illustrative active electrode 202 of the wand 102 electrically couples to terminal 724 of the voltage generator 716 by way of the connector 120, and return electrode 204 electrically couples to terminal 726 of the voltage generator 716.

FIG. 8 shows a method in accordance with at least some embodiments. In particular, the method starts (block 800) and proceed to: flowing a conductive fluid within a fluid conduit disposed within a electrosurgical wand, the conductive fluid discharges through a plurality of discharge apertures and flows past a return electrode disposed distally from the fluid conduit, and is then discharged over an active electrode (block 802); applying electrical energy between the active electrode and the return electrode (block 804); forming, responsive to the energy, a localized plasma proximate to an edge feature disposed on the active electrode (block 806); ablating, by the localized plasma, a portion of a target tissue proximate to the edge feature (block 808); and heating, responsive to the energy, the target tissue at locations spaced away from the edge feature to thereby provide concomitant hemostasis (block 810). And thereafter the method ends (block 812).

In addition to arthroscopic, otolaryngological, and spinal procedures, the ability to provide a device according to certain embodiments described herein for the fine dissection of soft tissue using electrosurgical techniques is also desirable in head and neck, gastrointestinal, urological, gynecological, and general surgical procedures. FIG. 9 illustrates a perspective view of an alternative embodiment for a distal end 908 of a wand 902 in accordance with at least some embodiments. A portion of the elongate shaft 906 may be made of a metallic material (e.g., Grade TP304 stainless steel hypodermic tubing). In other embodiments, portions of the elongate shaft 906 may be constructed of other suitable materials, such as inorganic insulating materials. The elongate shaft 906 may define a circular cross-section at the handle or proximal end (not shown here, but similar to previously described embodiments), and at least a portion of the elongate shaft 906 at the distal end 908 may be flattened to define an elliptical, oval or semi-circular cross-section.

Still referencing FIG. 9, distal end 908 may further comprise a non-conductive spacer 1000 coupled to the elongate shaft 906. In some cases the spacer 1000 is ceramic, but other non-conductive materials resistant to degradation when exposed to plasma may be equivalently used (e.g., glass). The spacer 1000 supports electrodes of conductive material, with illustrative active electrode labeled 1002 in FIG. 9. Active electrode 1002 defines an exposed surface area of conductive material, where active electrode 1002 is approximately a thin plate or thin sheet of particular thickness T. For embodiments using this sheet or plate, the plate or sheet may be molybdenum, titanium, tungsten, other suitably conductive material having a thickness between and including 0.010 inches and 0.020 inches, and more preferably of 0.013 inches, and having an exposed standoff distance (X) away from the spacer 1000 of approximately 0.030 inches to 0.050 inches. Standoff distance X may be seen more clearly in FIG. 10A and FIG. 11B, and is sufficiently sized so as to extend adequately beyond the spacer 1000 and shaft 906, to allow the user to observe the distal tip of active electrode 1002 during use. Spacer 1000 may have a tapered feature 1001 as shown more clearly in FIG. 11B, which serves to improve visibility of the active electrode 1002 during use in a coagulating orientation (FIG. 11B). Tapered feature 1001 may also improve fluid flow between the active electrode 1002 and return electrode 1004. Spacer 1000 is tapered so as to be thicker adjacent to the return electrode 1004 and thinner adjacent the active electrode 1002, so as to provide an incline to ease the flow of any fluid from the vicinity of the return electrode 1004 to the active electrode 1002. Further, spacer 1000 may define an elliptical or semi-circular cross-section to provide a flattened support profile for active electrode 1002.

In certain embodiments, the active electrode 1002 has at least one inverted cusp 1003 at a specific, distinct location advantageous for enhanced plasma formation when wand 902 is in certain orientations, as will be described in later figures. In FIG. 9 and FIG. 10A, three inverted cusps are shown, 1003 a, 1003 b, and 1003 c. In particular, active electrode 1002 may be defined by at least one inverted cusp 1003, with the at least one inverted cusp 1003 being defined by two curved portions that intersect at a point 1018, so as to create a surface asperity, spaced proximally away from the active electrode distal surface 1020. As shown in FIG. 9, inverted cusps 1003 a, b and c have a consistent or uniform shape throughout the thickness T of active electrode 1002, so that the point of intersection 1018 of the two smooth curves creates an elongated surface asperity (line), through the thickness T of electrode, a constant depth below the tissue contacting surface of the active electrode. The at least one inverted cusp 1003 a, b, c creates an asperity or point of plasma initiation to improve plasma formation proximate the point of intersection 1018 for smooth tissue cutting. Unlike other plasma initiating asperities known in the art, such as externally protruding points or alternatively edges or corners of electrodes, the inverted cusp provides a plasma initiation point that minimizes tissue snagging during electrode motion across tissue surfaces during treatment of tissue. The at least one inverted cusp 1003 creates a plasma initiation location that is spaced away from tissue. Inverted cusp 1003 may have a depth measured from surface 1020 to intersection 1018 between and including 0.005 and 0.015 inches, and more preferably of approximately 0.010 inches.

Active electrode 1002 may also include a superior surface 1005 a and inferior surface 1005 b, with 1005 b shown in FIG. 9 and FIG. 10A. Surfaces 1005 a and 1005 b are a second, distinct location away from inverted cusps 1003 a, 1003 b and 1003 c, and are generally flat and free of any asperities, and thereby more adapted for conductive/resistive heating of tissue at locations spaced away from inverted cusps 1003. Conductive heating of surrounding tissue may provide concomitant hemostasis of small blood vessels while plasma is initiated for cutting. Surfaces 1005 a and 1005 b may also provide for a more pure hemostatis tissue effect with minimal tissue cutting, when wand 902 is in the orientation as shown in FIG. 11B that will be explained in more detail later.

Wand 902 may also include a return electrode 1004 for completing the current path between active electrode 1002 and controller 104 (not shown here). Return electrode 1004 is preferably a semi-annular member, defining a portion of the exterior of shaft 906, and a distal portion of return electrode 1004 is preferably exposed. Return electrode 1004 is suitably connected to controller 104. At least a proximal portion of return electrode 1004 is disposed within an electrically insulative sheath 1006, which is typically formed as one, or more electrically insulative sheaths or coatings, such as polytetrafluoroethylene, polyimide, and the like. The provision of the electrically insulative sheath 1006 encircling over a portion of return electrode 1004 prevents direct electrical contact between return electrode 1004 and any adjacent body structure or the surgeon. Such direct electrical contact between a body structure (e.g., tendon) and an exposed common electrode member 1004 could result in unwanted heating and necrosis of the structure at the point of contact causing necrosis.

Return electrode 1004 is preferably formed from an electrically conductive material, usually metal, which is selected from the group consisting of stainless steel alloys, platinum or its alloys, titanium or its alloys, molybdenum or its alloys, and nickel or its alloys. Referring now to FIG. 10A, the inferior side of wand 902, return electrode 1004 is shaped so as to maintain a substantially constant distance Y between the proximal edge of active electrode 1002 and distal edge of return electrode 1004. As such, it is also preferable that the distal projection of return electrode 1004 and spacer 1000 have a non-uniform shape to approximate the geometry and curvature of active electrode distal surface 1020. In a preferred embodiment, return electrode 1004 has an extended feature in the form of a curved distal portion 1015 extending distally which brings the distal end of the return electrode 1004 closer to the targeted tissue to improve the conduction of current through tissue and saline between the active and return electrodes. This enables a more uniform and continuous delivery of electrical current through the targeted tissue during coagulation mode, providing greater depth of thermal penetration for improved coagulation of blood vessels. In addition, the distal profile of the return electrode 1004 is designed with a curvature that closely matches the curvature of the insulator material 1000 and the corresponding proximal and distal curvatures of the active electrode 1002. By keeping the curvatures of these edges similar, a uniform distance is maintained between the active and return electrodes. This results in a more uniform energy density being maintained at all portions of the active electrode, allowing plasma to form more readily at any point along the distal edge of the active electrode (i.e., uniform energy density provides equivalent areas where plasma can initiate anywhere along the electrode). This is particularly advantageous when different portions of the active electrode are used to cut/ablate tissue, such as when a physician changes the cutting direction and uses the opposite corner of the tip, or prefers to use the central portion of the electrode for precise, localized dissection.

In some embodiments saline is delivered to the distal end 908 of wand 902, to aid in plasma creation. Referring to FIG. 9, discharge apertures 1008 and 1009 are illustrated on the distal end 908, with a first plurality of apertures 1008 spaced both proximally from return electrode 1004 and active electrode 1002, and a second plurality of apertures 1009 spaced laterally relative to the return electrode 1004. Discharge apertures 1008 and 1009 are formed at the distal most point of the insulative sheath 1006, with the first plurality of discharge apertures 1008 defining the exposed portion of return electrode 1004. Insulative sheath 1006 further creates an annular gap along elongate shaft 906 between the insulative sheath and return electrode 1004, in which multiple axially disposed ribs are spaced equally throughout to form a plurality of fluid flow channels that direct discharged conductive fluid toward the return electrode 1004 and active electrode 1002. Discharge apertures 1008 and 1009 characterize the distal most opening of the associated plurality of flow channels. The discharge apertures 1008 and 1009 are fluidly coupled to the flexible tubular member 116 (FIG. 1) by way of a fluid conduit within the wand 902. Thus, saline or other fluid may be pumped into the flexible tubular member 116 (FIG. 1) and discharged through the plurality of fluid flow channels and discharge apertures 1008 and 1009 to further aid in developing consistent wetting around the circumference of return electrode 1004 and plasma generation around the active electrode 1002.

Fluid flowing from the first plurality of apertures 1008 flows across return electrode surface 1004 to adequately wet the exposed return electrode surface 1004, then flows down the tapered spacer 1000 and towards active electrode 1002. Discharge apertures 1008 are positioned so as to define a large enough surface area of return electrode 1004 during treatment of tissue for adequate tissue effect. Apertures 1008 partially encircle the exposed return electrode surface 1004, and may cooperate to flow fluid so that it creates a meniscus of fluid on return electrode surface 1004, even when wand is disposed in a substantially horizontal orientation where the return electrode 1004 is disposed horizontally or downwards, facing tissue as shown in FIG. 11B. When wand 902 is in the cutting orientation, as described later in FIG. 11A, the more distally disposed second plurality of apertures 1009 provide a more directed fluid supply to the outer edges of active electrode 1002 and cusps 1003 so as to improve plasma formation along the active electrode during cutting.

In yet still further embodiments, aspiration of fluid and ablative by-products is provided at the distal end 908 of the wand 902. FIG. 10B illustrates aspiration aperture 1022 (i.e., suction port 1022) at the distal end 908 of the device and disposed through the non-conductive spacer 1000 and defining in part an opening in return electrode 1004. FIG. 10B shows the superior side of wand 902. Similar in spirit for previously described embodiments, suction port 1022 is disposed at distal end 908 and in certain embodiments preferably only located on one side of spacer 1000. Suction port 1022 provides a conduit for aspiration of the area near the distal end 908, such as to remove excess fluids and remnants of ablation. Suction port 1022 is fluidly coupled to the flexible tubular member 118 (FIG. 1) by way of an aspiration conduit within the wand 902. Thus, saline or other fluid may be removed from the surgical site and preferentially directed around the active and return electrodes via suction port 1022 into the flexible tubular member 118 (FIG. 1) and discharged into a facility receptacle to further aid in visibility at the surgical site and in developing consistent wetting around the circumference of return electrode 1004 and plasma generation around the active electrode 1002.

The location of suction port 1022 further provides directed fluid flow of conductive fluid for ample wetting of the active and return electrodes on the opposing side of the tip, with the saline flowing down from discharge apertures 1008 and 1009, in particular from the on the non-suction (inferior) side of the shaft, around the active electrode tip, then pulled back up on the superior side of the wand toward suction port 1022. Applicants have found it is particularly beneficial to direct conductive fluid flow to discrete areas away from the suction port 1022 to provide broader wetting of the exposed surface of return electrode 1004, enabling more uniform plasma formation. The distal portion of the return electrode 1004 on the superior side of wand 902 mimics the shape of the return electrode on the inferior side, as much as possible, with the interruption of the suction port 1022 resulting in a modified profile. Similar in shape to the portion of return electrode 1004 on the superior side, two extended features in the form of two curved distal portions 1023 a and b result, due to the inclusion of the suction port 1022. These extended features 1023 a, b allow the return electrode 1004 to extend distally and closer to the targeted tissue to improve the conduction of current through tissue and saline between the active and return electrodes. This enables a more uniform and continuous delivery of electrical current through the targeted tissue during coagulation mode, providing greater depth of thermal penetration for improved coagulation of blood vessels.

Similar to embodiments described earlier, return electrode 1004 is not directly connected to active electrode 1002. To complete a current path so that active electrode 1002 is electrically connected to return electrode 1004 in the presence of a target tissue, electrically conducting liquid (e.g., isotonic saline) is caused to flow along liquid paths emanating from discharge apertures 1008 and 1009 and contacting both return electrode 1004 and active electrode 1002. When a voltage difference is applied between active electrode 1002 and return electrode 1004, high electric field intensities will be generated at the distal tip of active electrode 1002, and more preferentially at cusps 1003, with current flow from active electrode 1002 to the return electrode 1004, the high electric field intensities causing ablation and tissue treatment of target tissue adjacent the distal tip of active electrode 1002.

FIG. 11A shows the wand distal end 908 in an orientation so as to preferably ablate and/or dissect a target tissue 1030, with some concomitant hemostasis. At least one inverted cusp 1003 is shown in contact with target tissue 1030. Fluid 2008 is discharged from the first plurality of apertures 1008, passing over return electrode 1004, over spacer 1000 and wetting active electrode 1002. Fluid 2009 is also discharged more directly towards cusp 1003 from the second plurality of discharge apertures 1009, so as to aid preferential plasma initiation at cusp 1003 and enhanced ablative tissue effect.

FIG. 11B shows a wand distal end 908, in an orientation so as to preferably provide hemostasis to surrounding target tissue 1030. Inferior side of active electrode 1005 b can be seen in contact with tissue 1030, along length X. This orientation is preferential as it provides the larger surface area of return electrode 1004 in contact with tissue. Additionally, as described earlier, the shape of the return electrode 1004 on the inferior side together with the directional flow from discharge apertures 1008 may create a meniscus of fluid 2010 on the return electrode 1004, allowing for good wetting of return electrode 1004 even when placed in a substantially horizontal or inverted position as shown here. Tissue 1030 may preferably be in contact with active electrode 1002 along inferior side 1005 b, tapered feature 1001 and a portion of return electrode 1004 to achieve the desired tissue effect. Additionally, a small amount of target tissue may also be pressed within gap G, shown between active electrode 1002 and spacer 1000, which may also provide for a deeper thermal tissue effect in the tissue directly adjacent and within the gap G.

FIG. 12 shows a method in accordance with at least some embodiments. In particular, the method starts (block 1200) and proceed to: flowing a conductive fluid within a fluid conduit disposed within a electrosurgical wand, the conductive fluid discharges through a plurality of discharge apertures and a portion of the fluid flows over a return electrode disposed distally from the fluid conduit, and is then discharged over an active electrode while a portion of the fluid is discharged directly to the active electrode (block 1202); orienting said wand so as to place an inverted cusp feature on an active electrode directly on target tissue (block 1204); applying electrical energy between the active electrode and the return electrode and forming, responsive to the energy, a localized plasma proximate to said cusp (block 1206); ablating, by the localized plasma, a portion of a target tissue proximate to the cusp (block 808); and heating, responsive to the energy, the target tissue at locations spaced away from the cusp to thereby provide concomitant hemostasis (block 1210). And thereafter the method ends (block 1212). The method may further include repositioning the wand so as to place the inferior side of an active electrode directly in contact with target tissue and re applying electrical energy between the active electrode and return electrode and heating, responsive to the energy, the target tissue adjacent to the active electrode to provide hemostasis.

The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications possible. For example, while in some cases electrodes were designated as upper electrodes and lower electrodes, such a designation was for purposes of discussion, and shall not be read to require any relationship to gravity during surgical procedures. It is intended that the following claims be interpreted to embrace all such variations and modifications.

While preferred embodiments of this disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching herein. The embodiments described herein are exemplary only and are not limiting. Because many varying and different embodiments may be made within the scope of the present inventive concept, including equivalent structures, materials, or methods hereafter though of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense. 

What is claimed is:
 1. An electrosurgical wand comprising: an elongate shaft that defines a handle end and a distal end; a connector comprising a first and second electrical pins; an insulative sheath having a distal end that defines a first and second plurality of discharge apertures on the distal end of the elongate shaft, the first and second plurality of discharge apertures fluidly coupled to a first fluid conduit, and the first fluid conduit within the elongate shaft; a first active electrode of conductive material disposed on the distal end of the elongate shaft, the first active electrode having a distal surface and a thickness, and wherein the distal surface comprises at least one inverted cusp portion, defined by two smooth curved surfaces and a line of intersection spaced proximally from the distal surface; and wherein the first active electrode is electrically coupled to the first electrical pin; a first return electrode of conductive material, the first return electrode comprising an a distally extending tab arranged on a first side of the shaft and having a shape selected so that the spacing between a distal edge of the tab and the distal surface of the active electrode is near-uniform along the length of the edge of the tab, the first return electrode electrically coupled to the second electrical pin; and at least one aspiration aperture on a second side of the elongate shaft fluidly coupled to a second fluid conduit, the second fluid conduit within the elongate shaft.
 2. The electrosurgical wand of claim 1, wherein the line of intersection has a uniform depth from the distal surface of the first active electrode.
 3. The electrosurgical wand of claim 1, further comprising a non-conductive spacer disposed between the first active electrode and the return electrode, and wherein the spacer is tapered to improve fluid flow from return electrode to active electrode.
 4. The electrosurgical wand of claim 1 wherein the plurality of discharge apertures are fluidly coupled to a plurality of fluid flow channels disposed in an annular gap between the insulative sheath and the elongate shaft.
 5. The electrosurgical wand of claim 1, wherein the first and second plurality of discharge apertures encircle the elongate shaft.
 6. The electrosurgical wand of claim 1, wherein the first plurality of discharge apertures is spaced proximally from a distal extension of the first return electrode and partially encircle the return electrode.
 7. The electrosurgical wand of claim 1, wherein the second plurality of discharge apertures is disposed on at least one lateral side of the wand and proximate at least one inverted cusp, so that the fluid discharged from the second plurality of discharge apertures is directed towards the at least one inverted cusp without flowing over the return electrode.
 8. The electrosurgical wand of claim 1, wherein the first active electrode further comprises a substantially smooth portion, free of any surface asperity, operable to provide a hemostatic tissue effect to target tissue.
 9. The wand of claim 1, wherein the first plurality of discharge apertures are disposed on the first side and the second plurality of discharge apertures are disposed laterally relative to the first and second side.
 10. A system comprising: an electrosurgical controller, the electrosurgical controller configured to produce radio frequency (RF) energy at an active terminal with respect to a return terminal; an electrosurgical wand coupled to the electrosurgical controller, the electrosurgical wand comprising: an elongate shaft that defines a handle end and a distal end; an insulative sheath disposed along a portion of the length of the elongate shaft and having a sheath distal end defining a first and second plurality of discharge apertures, the first and second plurality of discharge apertures fluidly coupled to a first fluid conduit and operable to deliver an electrically conductive fluid through the discharge apertures to the shaft distal end; a first active electrode of conductive material disposed on the distal end of the elongate shaft, the first active electrode having at least one surface asperity for enhanced tissue cutting capability and a smooth portion for coagulating capabilities, and the first active electrode electrically coupled to the first electrical pin; a first return electrode of conductive material, the first return electrode comprising an extended feature disposed a substantially constant distance from the first active electrode, and the first return electrode electrically coupled to the second electrical pin; and an aspiration aperture on the distal end of the elongate shaft fluidly coupled to a second fluid conduit, the second fluid conduit within the elongate shaft; wherein the first plurality of discharge apertures are disposed proximally from the return electrode extended feature and partially encircle a proximal and lateral portion of the return electrode; and wherein the second plurality of discharge apertures is disposed on at least one lateral side of the wand and adjacent at least one surface asperity so that fluid discharging from the second plurality of discharge apertures flows directly to the at least one surface asperity.
 11. The electrosurgical wand of claim 10, wherein the active electrode has a thickness, and wherein the at least one surface asperity is an inverted cusp, disposed through the entire active electrode thickness.
 12. The electrosurgical wand of claim 11, wherein the at least one inverted cusp portion is defined by two smooth curved portions, so that the active electrode moves smoothly over target tissue, and wherein a line of intersection of the two smooth curved portions is disposed proximally from a tissue contacting surface of the active electrode.
 13. The electrosurgical wand of claim 10, wherein the first and second plurality of discharge apertures are fluidly coupled to a plurality of fluid flow channels disposed in an annular gap between the insulative sheath and the elongate shaft.
 14. The electrosurgical wand of claim 10, wherein the return electrode is disposed distal to the first plurality of discharge apertures and laterally relative to the second plurality of discharge apertures.
 15. A method comprising: flowing a conductive fluid within a fluid conduit disposed within a electrosurgical wand, the conductive fluid discharges through both a first plurality of discharge apertures and a second plurality of discharge apertures; discharging the fluid from the first plurality of discharge apertures over a return electrode, and then over an active electrode, while concomitantly discharging the fluid from the second plurality of discharge apertures directly over the active electrode, bypassing the return electrode; orienting the wand so that an inverted cusp portion of the active electrode is in contact with a target tissue; applying electrical energy between the active electrode and the return electrode; forming, responsive to the energy, a localized plasma proximate to the inverted cusp portion; ablating, by the localized plasma, a portion of a target tissue proximate to the inverted cusp portion; and heating, responsive to the energy, the target tissue proximate to a smooth portion disposed on the active electrode at locations spaced away from the inverted cusp portion to thereby provide concomitant hemostasis.
 16. The method of claim 15, further comprising aspirating through a fluid conduit in the electrosurgical wand, the aspirating disposed in discrete areas away from a substantial portion of the discharge apertures so that discharged fluid flows over a substantial portion of the return electrode and active electrode, to provide broader wetting of the exposed surface of return electrode, enabling more uniform plasma formation.
 17. The method of claim 15, wherein the return electrode comprises a distally extending tab arranged on a first side of the shaft and having a shape selected so that the spacing between a distal edge of the tab and a distal apex of the active electrode is uniform along the length of the edge of the tab.
 18. The method of claim 15, further comprising the steps of; re-orienting the wand so that the smooth portion of the active electrode is substantially in contact with the target tissue; applying electrical energy between the active electrode and the return electrode; forming, responsive to the energy, a localized plasma proximate to the smooth portion of the active electrode; and heating, responsive to the energy, the target tissue proximate to the smooth portion to provide hemostasis.
 19. The method of claim 18, further comprising the step of pressing the target tissue within a space disposed between the active electrode and a non-conductive spacer while applying energy, so as to create a focused point of heating, responsive to the energy, and a deeper localized thermal effect into the target tissue.
 20. The method of claim 18, wherein re-orienting the wand causes a substantial portion of the return electrode to be inverted and wherein the first plurality of discharge apertures partially encircle both proximal and lateral sides of the return electrode so that the fluid flows so as to wet the return electrode and form a meniscus on the return electrode, even when inverted.
 21. The method of claim 15, wherein fluid from the second plurality of discharge apertures bypasses the return electrode, flows directly over a non-conductive spacer and proximate the inverted cusp portion of active electrode.
 22. The method of claim 15, wherein the active electrode is a thin plate extending distally from a wand distal end, the thin plate active electrode having an exposed standoff surface and a thickness, and wherein the step of discharging further comprises discharging fluid from the second plurality of apertures substantially towards the active electrode thickness and discharging fluid from the first plurality of apertures substantially over the exposed standoff surface.
 23. The method of claim 22, wherein an inverted cusp is disposed on a surface defined by the active electrode thickness, the inverted cusp adjacent the second plurality of discharge apertures. 